2012

Optimizing Finite Element Material Models in a Crash Test Dummy

Lumbar Spine Validation

As an example of the component testing, consider the experiment and simulation of the lumbar spine assembly. The test configuration and model are shown in Figure 4. The lumbar spine is a critical component in the dummy as it plays a significant role in the upper body kinematics under lateral impact loads. Sledtype impulse tests were conducted for the validation of the lumbar spine.

The rubber lumbar spine is in an initial state of compression due to the weight of the thorax surrogate with a mass of 4.85 kg. The component is fixed at the bottom to a moving base. Sled acceleration pulses of 20 g and 35 g were applied separately in the lateral direction to simulate side impact. The tests were repeated for an angle of 90 degrees from the direction of travel (direct side impact) and at an angle of 60 degrees (oblique side impact).

A representative collection of output signals was obtained for one of the tested configurations: an impulse acceleration of 20 g applied to the base in the horizontal plane at a 60-degree angle with respect to the direction of travel. The output is measured by the lumbar spine load cell located at the center of the sacrum block (colored brown in Figure 4). The level of correlation between the simulation and experimental results clearly demonstrates that the finite element model of the lumbar spine using optimized material properties can realistically capture the shear and bending behavior induced by side impact loading.

Conclusions

Design automation and optimization software is a powerful tool for calibrating finite element analysis material models. By automating the process of fitting material model coefficients to experimental data, time is saved and accuracy may be increased. Successful calibration of a linear viscoelastic material model for the behavior of rubber-like materials has been demonstrated.

This article was written by George Scarlat, Engineering Specialist (Crashworthiness and Occupant Safety), and Sridhar Sankar, Manager, Automotive Engineering Specialists, at Dassault Systèmes SIMULIA, Providence, RI. For more information, visit http://info.hotims.com/40436-121.

Reference

1. International Organization for Standardization,
International Standard 15830: Road
Vehicles- Design and performance specifications
for the WorldSID 50th percentile male
side-impact dummy, Geneva, 2005.

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